The present invention relates to an image pickup device and a method for driving the image pickup device.
Conventionally, image pickup devices such as CCD image sensors have been widely used for image scanners, facsimiles, digital cameras etc. JP-A-2001-157119 discloses an image pickup device in which a plurality of photo receiving units are arranged in parallel and each of the photo receiving units is configured in a manner that cells each for generating electric charges through photoelectric conversion are arranged in series.
An object of reading a document by lowering the resolution in the main scanning direction is to read the document at a high speed. Thus, it is required to make the frequency of shift pulses applied to a transfer unit higher as the resolution is made lower. However, there is a problem that the maximum frequency of the shift pulses is limited and, in general, a manufacturing cost increases when mounting a driving circuit for applying the shift pulses of a high frequency to the transfer unit. Further, in general, when the frequency of the shift pulses is determined, the frequency of output gate pulses is also determined in accordance with the determined frequency of the shift pulses. Thus, when the frequency of the shift pulses can not be made higher, the reading speed at a low resolution can not be made higher.